Certain C-glycosides compounds have demonstrated beneficial biological properties, in particular for combating ageing of the epidermis, and/or combating drying out of the skin. This is in particular the case with the compounds described in patent application WO-02/051828. These compounds act through stimulating the synthesis of glycosaminoglycans containing a D-glucosamine and/or N-acetyl-D-glucosamine residue, and are represented by formula (F):
in which S represents a monosaccharide or a polysaccharide, R represents various linear or cyclic radicals, and the group X can represent a group chosen from: —CO—, —CH(NR1R2)—, —CHR′— and —C(═CHR′)—, it being possible for R′ to represent various radicals, including the hydroxyl radical.
When R′ is a hydroxyl radical, the corresponding compound of formula (F) corresponds to formula (F2):
and has an asymmetric carbon, possibly existing in two epimeric forms R and S.
Taking into consideration also the fact that the sugar S can be linked to the side chain via an α or β linkage, the compound that results therefrom, of formula (F3):
can be in the form of 4 diastereoisomers denoted: (α, S); (α, R); (β, S); and (β, R).
The compounds of formula (F3) have up until now been described in the form of mixtures of several diastereoisomers. In particular, application WO-02/051828 discloses a process of synthesis that makes it possible to produce the compounds in the form of a mixture of diastereoisomers:

(β, S); (β, R) or (α, S); (α, R)
No method has made it possible to bring about the production of one of the forms in the diastereoisomerically pure state.